Abstract: A novel rice straw biochar/ attapulgite composite (BA) was prepared by pyrolysis under anoxic conditions with rice straw and attapulgite, which was modified with sodium hydroxide to improve its adsorption performance. Batch adsorption experiments, including adsorption kinetics, isothermal adsorption and change of initial pH, were conducted to investigate the adsorption behavior of composite materials in single and binary pollution systems of Cd and Pb. SEM-EDS, BET, FTIR, XRD, and XPS were used to analyze the adsorption mechanisms of modified composites of Cd and Pb. The results show that the adsorption capacity of sodium hydroxide modified composite (NBA) for Cd²⁺ and Pb²⁺ was 117.05 and 274.65 mg·g^-1, respectively, and the removal efficiency of NBA was increased by 31.2% and 51.7%, respectively, compared with BA. In the binary metal system, the adsorption capacity of NBA was also significantly better than that of BA. The pseudo-second-order kinetics model and the Langmuir isotherm model could describe the Cd²⁺ and Pb²⁺ adsorption processes of the composites better, which proves that the adsorption is mainly a single molecule chemical adsorption process. In addition, competitive adsorption analysis showed that Pb²⁺ was more easily adsorbed by composite materials than Cd²⁺ in coexisting solutions. The characterization method determined the adsorption mechanism of NBA for Cd²⁺ and Pb²⁺, mainly including the complexation with surface functional groups, precipitation with minerals and π-electron interaction. In conclusion, NBA is a highly potential adsorption material for the treatment of heavy metal pollution in wastewater.